Re: [PATCH v3 2/7] mm/lruvec: add irqsave flags into lruvec struct

[Shakeel Butt]

On Fri, Nov 15, 2019 at 7:15 PM Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> wrote:
>
> We need a irqflags vaiable to save state when do irqsave action, declare
> it here would make code more clear/clean.
>
> Rong Chen <rong.a.chen@xxxxxxxxx> reported the 'irqflags' variable need
> move to the tail of lruvec struct otherwise it causes 18% regressions of
> vm-scalability testing on his machine. So add the flags and lru_lock to
> both near struct tail, even I have no clue of this perf losing.

Regressions compared to what? Also no need to have a separate patch.

>
> Originally-from: Hugh Dickins <hughd@xxxxxxxxxx>
> Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Wei Yang <richard.weiyang@xxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Arun KS <arunks@xxxxxxxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
> CC: Rong Chen <rong.a.chen@xxxxxxxxx>
> Cc: cgroups@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  include/linux/mmzone.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index a13b8a602ee5..9b8b8daf4e03 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -269,6 +269,8 @@ struct lruvec {
>         unsigned long                   flags;
>         /* per lruvec lru_lock for memcg */
>         spinlock_t                      lru_lock;
> +       /* flags for irqsave */
> +       unsigned long                   irqflags;
>  #ifdef CONFIG_MEMCG
>         struct pglist_data *pgdat;
>  #endif
> --
> 1.8.3.1
>